Hilo

Today: Mostly cloudy with showers likely. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to around 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 88 near the shore to around 70 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 72 to 77 near the shore to 50 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 85 to 90 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs 65 to 86. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 80 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs 65 to 86. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 69 to 80 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 67 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 75 near the shore to around 54 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy with showers likely. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to around 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 87 near the shore to 65 to 72 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 85 to 90 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Isolated showers in the evening. Lows around 76 near the shore to 52 to 58 above 4000 feet. Southeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 85 to 90 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy easterly trade winds will continue through the week. Clouds and showers will favor windward and mauka locations, especially overnight through morning hours as pockets of moisture move through. High clouds will stream overhead at times through mid-week before diminishing during the latter portion of the week. The trades may ease slightly this weekend as a ridge to the north weakens.

Discussion

A surface trough 770 miles west of Kauai and the parent upper level low is generating a stream of high clouds over much of the island chain as seen in infrared satellite imagery. A surface high 1500 miles northeast of the state is generating breezy trades. Radar imagery shows areas of isolated to scattered showers riding in with the trades and focusing over windward and mauka regions which should become more isolated this afternoon. Inversion heights from early this morning were around 8-9 kft which is allowing for a few stray showers to spill over to leeward areas of the smaller islands.
As an upper trough west of the islands rotates eastward through mid-week, southwesterly flow aloft will increase high clouds over the state from west to east over the next couple of days. These high clouds should diminish through the second half of the week as upper heights rise and the flow shifts as a new low aloft develops further to the west. A breezy easterly trade wind pattern will persist through the week as the surface high remains far northeast. Tradewind clouds and showers will favor mainly windward and mauka locations, with the best chances during the overnight through morning hours as pockets of moisture move through. Cloud buildups and a few showers will also be possible along the Kona slopes of the Big Island from late morning through early evening each day as a result of daytime upslope flow. Although a few showers may make it into leeward areas on the other islands from time to time, rainfall accumulations will be light.
By the weekend, guidance shows the surface high far northeast of state weakening as a front develops and moves south. A new high will build to the far northwest. This pattern will ease trade wind speeds into the moderate range over the weekend into early next week.

Aviation

Moderate to locally breezy trade winds will persist. Radar continues to show scattered showers embedded in the trades moving into windward sections of the islands early this morning. This shower activity will continue to impact the windward and mauka areas through mid morning, become more isolated during the day, then pick back up overnight tonight. While most leeward locations will remain dry with the exception of an occasional spillover shower, the leeward section of the Big Island will likely see an increase in clouds and showers during the afternoon hours today. MVFR conditions will be possible with any passing showers across the islands, but VFR conditions will generally prevail.
AIRMET Sierra is in effect for mountain obscuration on the Big Island and may be needed through mid morning today as clouds and showers continue to pile up mainly on leeward slopes.

Marine

Fresh to strong easterly trade winds will persist through the week, which supports the Small Craft Advisory in effect for the windier channels and waters surrounding Maui County and the Big Island. This advisory may need to be expanded to other waters late Thursday through Friday as the pressure gradient tightens over the state. Guidance does depict a weakness forming in the ridge far north of the area by the end of the weekend, which would result in the trades easing slightly over the weekend into early next week.
Surf along south facing shores will remain up through the week as overlapping south to southwest long-period swells move through. Observations from the nearshore buoys reflect the current south swell down to around 2 ft at 12 seconds this morning. As this swell steadily eases today, a new long-period small southwest swell should begin showing up by the end of the today, which will be enough to keep the surf up at background levels through midweek. A similar southwest pulse is expected over the weekend.
Surf along north and west facing shores could come up slightly over the weekend as a medium-period north-northwest swell arrives. Otherwise, trade wind wrap into some northern exposures will be the only source for surf this week.
Surf along east facing shores will remain small and choppy through the week due to the local and upstream trade winds.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov